1. Field of the Invention
The present invention relates to a phase modulator circuit for producing from a reference signal several types of signals with different phase differences.
2. Description of the Related Art
In general, in the past, signal processing has been designed based on the assumption of completely synchronous processing. The clock signal in the circuit was used for all processing events on the time axis. Therefore, it was difficult to establish a processing timing of a time shorter than the clock frequency, for example. Accordingly, to produce such a shorter processing timing, use was made of the method of raising the clock frequency. The method of producing processing timings by raising the clock frequency, however, had the problem of increasing the power consumption.
Further, in the past, use has been made of delay elements using capacitors C and resistors R to produce timings shorter than the clock frequency or timings indivisible by whole multiples of the clock frequency. The method of using delay elements suffered from the problem that the constant changed several tens of percent when the delay times are generated in an LSI and further changed considerably due to temperature and the voltage of the power source, so a stable amount of delay could not be obtained.